Ginkgo bilobia (maidenhair tree)
This lonely tree, the only surviving member of a very ancient ancestry, is now classified in its own division, the Ginkgophyta, comprising the single class Ginkgoopsida, the single order Ginkgoales, the single family Ginkgoaceae , and the single genus Ginkgo, and this is the only species within the genus. Its relatives became extinct sometime before 200 million years ago; about the time that the first recognisable fossils of Ginkgo have been found, which is why it is sometimes referred to as the fossil tree.
How has it survived? Well, it is very tough and lives a long time, possibly as long as two thousand years. It seems to have a liking for stream banks, rocky slopes and the edge of cliffs. It has a great propensity for vegetative reproduction, sometimes sprouting from the base of the trunk, or perhaps by growing aerial roots, so that if it falls victim to soil erosion it can re-establish itself from where these roots contact the earth. That is survival. It is also worth noting that six Ginkgos were the only living things to survive within two km of the atomic bomb that was dropped on Hiroshima.
How has it survived? Well, it is very tough and lives a long time, possibly as long as two thousand years. It seems to have a liking for stream banks, rocky slopes and the edge of cliffs. It has a great propensity for vegetative reproduction, sometimes sprouting from the base of the trunk, or perhaps by growing aerial roots, so that if it falls victim to soil erosion it can re-establish itself from where these roots contact the earth. That is survival. It is also worth noting that six Ginkgos were the only living things to survive within two km of the atomic bomb that was dropped on Hiroshima.
The Red List classifies Ginkgo as endangered, noting that, although it has been extensively grown in cultivation for several centuries (and still is), its wild population is small and restricted to Xitianmu Mt., Zhejiang, China.
As a decorative plant it is said to be easy to cultivate, requiring good sunlight, well-drained soil and plenty of water. It drops its leaves suddenly (in less than 15 days) at the onset of winter, when it is frost resistant. It is also a good subject for bonsai. Seed is easy to germinate. Plants or seed offered for sale are the product of years of experience, and are excellently suited to cultivation. Usually, it is the male tree that is propagated because the fruits produced by the female are, to put it politely, malodorous (smells like rancid butter).
Ginkgos reach a height of 20-35m, with some specimens in China being over 50m . Like the Kauri, juveniles grow tall and slender; the tree branches out to form a crown after it has grown above the forest canopy.
Ginkgos are either female or male. Male plants produce small pollen cones. In female plants two ovules are formed at the end of a stalk. Pollen reaches the ovules and is kept in a pollen chamber and stored there awaiting the time for fertilisation. It then grows into two sperms which are released from the chamber so that they can swim up a narrow channel to fertilise the ovule. It is not known if the seed is fertilised before or after it falls.The seed is 1.5-2 cm long. Its fleshy outer layer is light yellow-brown, soft, and fruit-like and attractive in appearance.
You can distinguish a Ginkgo from other gymnosperms by its fan-shaped and bilobed leaves. All Ginkgo trees have a relatively primitive vascular system. The veins continuously divide into twos. This vein pattern (dichotomous venation) is unique to the Ginkgo.
Fig 1 Female ovules waiting pollination.
Fig 3. Ripening fruit.
Fig 1 is from Wikipedia Photographed by IMC and made available under CCA licence.
Figs 2 & 3 are by Steve Nix from http://forestry.about.com/od/forestphotogalleries/
Fig 2 Male cones
One of the six Ginkgo soon after the A-bomb blast. Today it is still alive and in perfect health.
